1. Field of the Invention
This invention relates to strong, soft, absorbent paper webs and to the processes for making them. 2. Background Art
One pervasive feature of daily life in modern industrialized societies is the use of disposable products, particularly disposable products made of paper. Paper towels, facial tissues, sanitary tissues, and the like are in almost constant use. Naturally, the manufacture of items in such great demand has become, in the Twentieth Century, one of the largest industries in industrially developed countries. The general demand for disposable paper products has, also naturally, created a demand for improved versions of the products and of the methods of their manufacture. Despite great strides in paper making, research and development efforts continue to be aimed at improving both the products and their processes of manufacture.
Disposable products such as paper towels, facial tissues, sanitary tissues, and the like are made from one or more webs of tissue paper. If the products are to perform their intended tasks and to find wide acceptance, they, and the tissue paper webs from which they are made, must exhibit certain physical characteristics. Among the more important of these characteristics are strength, softness, and absorbency.
Strength is the ability of a paper web to retain its physical integrity during use.
Softness is the pleasing tactile sensation the user perceives as he crumples the paper in his hand and contacts various portions of his anatomy with it.
Absorbency is the characteristic of the paper which allows it to take up and retain fluids, particularly water and aqueous solutions and suspensions. Important not only is the absolute quantity of fluid a given amount of paper will hold, but also the rate at which the paper will absorb the fluid. When the paper is formed into a device such as a towel or wipe, the ability of the paper to cause a fluid to preferentially be taken up into the paper and thereby leave a wiped surface dry is also important.
An example of paper webs which have been widely accepted by the consuming public are those made by the process described in U.S. Pat. No. 3,301,746 issued to Sanford and Sisson on Jan. 31, 1967. Other widely accepted paper products are made by the process described in U.S. Pat. No. 3,994,771 issued to Morgan and Rich on Nov. 30, 1976. Despite the high quality of products made by these two processes, the search for still improved products has, as noted above, continued. The present invention is a noteworthy fruit of that search.